The Islamic Personality by Sheikh Taqīuddīn An-Nabahānī

Jihad is an absolute obligation, and it is not restricted or conditional upon anything. The ayah concerning it is absolute:

The presence of the Khalifah has no interference upon the obligation of jihad; rather jihad is obligatory whether there is a Khalifah or not. However, when there is a Khalifah whose Khilafah has been contracted legally and who has not left it for any reason, the matter of jihad is delegated to the Khalifah and his ijtihad as long as he is the Khalifah even if he was wicked as long as he remains in the headquarters of the Khilafah. The citizens are obliged to obey his opinion over this even if he were to command any one of them to fight together with a wicked Amir due to what Abu Dawud narrated with his chain from Abu Hurairah (ra): The Messenger of Allah (saw):

It is obliged upon the Muslims’ Khalifah to expend his effort at every time to go out personally or send Muslim armies or expeditions, then be confident in the beautiful promise of Allah (swt) to support him in Allah’s statement:

He is obliged to begin organizing the army in the country’s extremities so as to be sufficient against those who they are facing from the disbelievers. It is not allowed for the Khalifah to leave any frontier empty of a group of Muslims who are sufficient to fight the enemy; rather it is obligatory that all frontiers be packed with the Islamic army at all times. It is obliged that he establishes all that will defend the Muslims and the Muslims’ land from the enemy’s harm such as fortresses, trenches or anything, and it is obliged that he prepares what he can of all types of strength to protect the Islamic State and Islamic land from the disbelievers and their conspiracies.

It is obliged that the Khalifah personally supervises the practical leadership of the army in its military policy and administration. When he places upon it a leader with military expertise he only places him as his representative, since the Khalifah is not only Allah commander of the army but rather its practical leader. The Messenger (saw) supervised the army leadership himself, and when he would send expeditions would do so in his capacity as an army leader. Umar (ra) would send detailed information to his leaders in Persia and Sham which indicates that the Khalifah is the army’s leader practically. His obedience is obligatory upon every individual in the army whether he is a soldier or leader, just the same as it is obligatory upon every individual citizen. Muslim has narrated from a chain of Abu Hurairah (ra) that the Prophet (saw) said:

The meaning of the Imam being a shield is (that he) is a shield because he prevents the enemy from harming Muslims. However the Khalifah should not command a decisive command that has no effect except within the people’s capability; if he knows that they will not be able to perform he does not command them with it strictly. Nor should he carry the Muslims to suicide, nor command them with something for which he fears betrayal from them.

This is when there is a Khalifah; if the Khalifah is absent, jihad is not delayed in any way whatsoever since its benefit disappears with its delay. If the Khalifah sends an army and commands over them an Amir who is killed or dies, then it is upon the army to appoint one of them as did the Prophet’s Sahabah in the army of Mu’tah upon which the Messenger (saw) consented. If the army has an Amir, none of the army can leave the camp for any purpose except with the Amir’s permission. And if he commands the doing of something or the leaving of something, his obedience is obligatory and it is forbidden to contradict him due to Allah’s statement:

What applies here to the Prophet applies to the Khalifah, and the Amir is measured by analogy upon the Khalifah and (also) due to his (saw) statement: